1) A ratchet is a mechanical device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. Though something of a misnomer, "ratchet" is also often used to refer to ratcheting socket wrenches, a common tool with a ratcheting handle.

2) A character in the Transformers franchise. (Seriously?)

1) There is a ratchet in that clock. That means that the clock can't turn the opposite direction...